2. Ipad 4th gen uses the new lightning port, which is alot slimmer than the old port, so you'll need a converter. Then everything should work as usual, I've never heard of ios software that isn't backwards compatible, only newer software not running on the old ios versions. Ipad4 comes with ios6 from the factory, the latest on mine is 6.1.3

The 1st gen has bad CPU and graphics capabilites compared to the later ones, so synths and programs made for the later ones suffer badly.

Not out of the box no, but there are adapters to interface with older outside gear that used the old port. It's just that it adds an extra lump at the bottom so if it's supposed to dock into the device it won't really sit without support. If it's just a plug on a chord there is no problem with it.

Beats me why they changed the connection port, but hey..Apple. The Mini uses it too, and all apple products from now on. They probably thought it's about time people throw away all their old speakers and dock gadgets and buy brand new overpriced ones.

As for the refurbished question, I see no issues with that as long as it has had a proper factory reset so that nothing hangs around from the previous owner.